Finishing and Painting 3D Printed Parts

Wednesday, October 26, 2016

With the high strength properties of continuous fibers and the surface finish of Onyx, beautiful, functional parts come right out of a Markforged printer. However, some applications require a slightly different aesthetic. We’ve previously covered dyeing nylon 3D printed parts, and now the Markforged team has been preparing some colorful office props for Halloween. Read on and learn our methods for painting 3D printed parts!

Finishing

Before painting your 3D printed parts parts they may require some finishing. This means smoothing the surface of your part out and making sure that there aren’t any rough features of the part that may prevent paint adhesion. Such features include residue left by support material, and strings or blobs of filament that may have been caused by low angle overhangs or material inconsistencies. If these occur, we suggest the following:

1. Cleaning off Glue:

If you have used our printer, you’ll know that laying glue down on your build plate before a print will vastly improve your printing results. Once you remove the part from the build plate, some glue residue is left on the part. Wash this residue off with some water and let it dry.

‍Wash the glue off your printed parts before any finishing or painting.

2. Trimming with Flush Cutters or Tweezers:

To get rid of small strings or blobs of filament that have built up, a pair of wire cutters or tweezers to clip or pick off inconsistencies will clear these off easily.

‍Trim inconsistencies off while being careful not to cut into the part itself.

3. Sanding:

If there are rough patches on your part, or you want to get rid of the well-known layer lines of FFF (Fused Filament Fabrication) printing, we advise wet sanding your 3D printed parts with 220 grit sandpaper. Wet sanding will clear scratches, blemishes, and bumps that may arise on your part. Because some of our materials contain carbon fiber, sand your parts in a well ventilated area with a mask.

‍Be careful not to over-sand: this will erode the wall, ceiling, or floor layers and all you’ll be left with is infill structure!

4. Removing Dust:

After sanding, some dust residue may remain on your part. To remove these fine particles, clean your part out with a wet scrub brush, making sure to get all the corners and cracks. Once your part is dry, you may want to use some tack cloth to get any remaining specks out.

Spray Painting

The process for spray painting 3D printed parts is very similar to spray painting most other plastics. Nylon turns out to be great for paint and varnish because it is a highly polar polymer. Unsurprisingly, paints specifically for plastics usually end up working the best for 3D printed parts. Usually Rust-Oleum or Krylon have a wide variety (in color and application) of paints that work on 3D printed plastics.

‍Paint in a well-ventilated area with gloves and a mask for protection.

1. Selecting Spray Paint:

Without primer both of our materials absorb paint, so a primer coat is necessary for our parts. Pick your primer and your paint, make sure they work on plastics, and you’re good to go!

2. Painting Precautions:

Make sure you spray paint and let your parts dry in a well-ventilated area – use a fume hood or spray booth if possible. Painting with a respirator and gloves is advised.

3. Setting Up Your Part:

Because 3D printed parts allow for complex, intricate geometries, you may want to hang your part from some wire or place it on a stand so that you can reach all or most of the part with paint without having to turn it over – many spray booths have these. However, if your painting space is limited or you are just painting outside, just place your part on some newspaper so that you don’t damage the surrounding area. If you are only painting a specific section or pattern onto your part, use painters tape to conceal the parts you don’t want painted.

4. Apply Primer Coat:

Spray the primer coat onto your 3D printed part. Different brands of primer have different suggestions as to technique, coats, and distance, so make sure you read them before painting! Make sure you cover all the areas you want to paint in primer – this may require letting the first coat dry before turning the part over to spray the back or underside of the part.

Primer will prevent the 3D printed part from absorbing paint.

5. Apply Finish Coat:

Once the primer coat is dry, spray the finish coat of spray paint onto your part as advised by the brand of paint you are using. If you apply too many coats or paint too close, you may drench the part and it will affect the quality of the paint job. Again, you may need to rotate or reorient the part to cover all faces.

‍Apply the finish coat and let it dry.

6. Let it Dry:

Let your part dry before final use and handling as recommended by the paint brand. After that, your part is good to go!

‍The finished 3D printed mask.

Hand Painting

1. Selecting Hand Paints:

While we haven’t tested all of the hand paints in the world, acrylic paint works pretty well with our plastics. As explained in the next step, you will also need primer for a base coating.

2. Eliminate Paint Absorption with a Primer Coat:

One of the issues with hand painting 3D printed parts is that the plastic absorbs a lot of the paint. Even when hand painting, a primer coat is really important for a clean final product. As instructed above, spray a base coat of primer onto your part before painting.

‍An Onyx part hand painted without primer. Many more coats will be needed to conceal the plastic.